an object thrown at a certain angle to the ground moves in a second path and falls back to the ground the initial and the final point of the path of the object lies on the same horizontal line what is the work done by the force of gravity on the object?

Gravitational force field is conservative force field. In conservative field ,

workdone to move the object from point p to point q is independent of path .

Workdone depends only on initial point and final point.

 

If an object moves in horizontal direction from point p to point q ,

workdone is zero because displacement of object is perpendicular to the direction of gravitational force.

 

If an object is thrown from point p with some angle θ to ground, then the object falls back to point q

so that point p and point q are at same level in horizontal direction.

 

Since gravitational force field is conservative field, workdone is also zero in this path because workdone

is independent of path and depends only on initial point and final point.

 

when the object is moving upwards to a height h, workdone W_u = +( m g h ) is done by the object utilizing its own kinetic energy.

Where m is mass of object and g is acceleration due to gravity . Once kinetic energy of objct is exhausted, gravitational field is

doing workdone W_d = - ( m g h )  on theobject to reach the ground. Hence net workdone is zero.

 

( Work is done by the object is positive . Work is done on the object is negative )